20 May Edward Snowden, an employee of defence contractor Booz Allen Hamilton at the National Security Agency, arrives in Hong Kong from Hawaii. He carries four laptop computers that enable him to gain access to some of the US government’s most highly-classified secrets.
1 June Guardian journalists Glenn Greenwald and Ewen MacAskill and documentary maker Laura Poitras fly from New York to Hong Kong. They meet Snowden in a Kowloon hotel after he identifies himself with a Rubik’s cube and begin a week of interviews with their source.
5 June The Guardian publishes its first exclusive based on Snowden’s leak, revealing a secret court order showing that the US government had forced the telecoms giant Verizon to hand over the phone records of millions of Americans.
6 June A second story reveals the existence of the previously undisclosed programme Prism, which internal NSA documents claim gives the agency “direct access” to data held by Google, Facebook, Apple and other US internet giants. The tech companies deny that they have set up “back door access” to their systems for the US government.
7 June Barack Obama defends the two programmes, saying they are overseen by the courts and Congress. Insisting that “the right balance” had been struck between security and privacy, he says: “You can’t have 100% security, and also then have 100% privacy and zero inconvenience.”
The Guardian reports that GCHQ has been able to see user communications data from the American internet companies, because it had access to Prism.
8 June Another of Snowden’s leaks reveals the existence of an internal NSA tool – Boundless Informant – that allows it to record and analyse where its data comes from, and raises questions about its repeated assurances to Congress that it cannot keep track of all the surveillance it performs on American communications.
9 June Snowden decides to go public. In a video interview he says: “I have no intention of hiding who I am because I know I have done nothing wrong.”
10 June Snowden checks out of his Hong Kong hotel.
12 June Hong Kong’s South China Morning Post publishes the first interview with Snowden since he revealed his identity. He says he intends to stay in the city until asked to leave and discloses that the NSA has been hacking into Hong Kong and Chinese computers since 2009.
14 June The Home Office instructs airlines not to allow Snowden to board any flights to the UK.
16 June The Guardian reports that GCHQ intercepted foreign politicians’ communications at the 2009 G20 summit.
20 June Top secret documents published by the Guardian show how US judges have signed off on broad orders allowing the NSA to make use of information “inadvertently” collected from domestic US communications without a warrant.
21 June A Guardian exclusive reveals that GCHQ has gained access to the network of cables which carry the world’s phone calls and internet traffic and is processing vast streams of sensitive personal information it shares with the NSA.
The US files espionage charges against Snowden and requests that Hong Kong detain him for extradition.
23 June Snowden leaves Hong Kong on a flight to Moscow. In a statement, the Hong Kong government says documents submitted by the US did not “fully comply with the legal requirements under Hong Kong law” and it had no legal basis to prevent him leaving.